The divalent cation, Ca2 ion, serves as a regulatory signal through which eukaryotic cells perceive and respond to both internal and external stimuli. A single protein, calmodulin (CaM), is the primary intracellular receptor for Ca2 ion in most tissues where it serves as a Ca-dependent activator of numerous enzyme systems. Various lines of evidence suggest that the deregulation of animal cell growth upon cellular transformation may involve the perturbation of Ca-CaM regulated enzyme systems. Clearly, the pleiotropic effects seen on cellular transformation suggest that major cascade regulation systems, possibly those regulated by CaM, are perturbed by the transforming principle. Studies described here to test this possibility include: 1) Determining the presence and relative levels of CaM and CaM binding proteins, particularly those of known enzymatic activity, in normal chick embryo fibroblasts (CEF) and CEF infected with wild-type (wt) and transformation deficient (td) mutants of Avian sarcoma viruses (ASV) under various conditions of growth; 2) Examining the phosphorylation state of CaM binding proteins in normal and transformed cells and testing them as potential src kinase substrates both in vivo and in vitro using O-tyrosylphosphorylation as an assay for src kinase specific phosphorylation; 3) Testing whether or not, pp60src, is regulated either directly by a Ca-dependent interaction with CaM or indirectly through CaM-dependent protein kinases; 4) Examining by HPLC the in vivo pool levels of nucleotides, NAD, and NADP in normal and virally transformed CEF under a variety of growth conditions to test for possible transformation dependent perturbation and/or CaM-dependent regulation; 5) Detailed analyses of NAD kinase in normal and transformed CEF for possible CaM dependent regulation and transformation dependent alteration; and 6) Examination of other enzymes of nucleotide biosynthesis, such as ribonucleotide reductase for regulation by CaM in normal and transformed CEF.